DGIST develops key photocatalyst technology to convert CO2 into methane fuel

South Korean researchers have developed a key photocatalyst technology capable of converting carbon dioxide — a primary driver of climate change — into methane, a next-generation fuel.

A research team led by In Su-il, a professor in the Department of Energy Engineering at DGIST (Daegu Gyeongbuk Institute of Science and Technology), worked with a team led by William Goddard at the California Institute of Technology to significantly boost the performance of a solar-powered photocatalyst that converts CO2 into methane. The teams combined two co-catalysts with distinct roles and identified the mechanism behind the catalyst's operation.

Carbon dioxide is one of the most representative greenhouse gases driving climate change. Attention has shifted in recent years beyond simply reducing CO2 emissions toward technologies that convert the gas into useful resources such as fuels and chemical feedstocks. Photocatalyst technology, which uses sunlight as its energy source, has drawn particular interest for its potential to transform CO2 into valuable materials. Existing CO2 photoreduction catalysts, however, have seen limited practical use due to inefficient charge transfer and slow multi-electron reaction rates.

The research team developed a ternary-structured photocatalyst designated Pt/TiO₂-MoSe₂, combining two-dimensional molybdenum diselenide (MoSe₂) and platinum (Pt) nanoparticles on the surface of titanium dioxide (TiO₂), a widely used photocatalyst material. The two co-catalysts were engineered to perform complementary roles, enabling electrons generated by light to be used efficiently in the CO2 reduction reaction.

MoSe₂ has a known limitation: it tends to aggregate or deform, making it difficult to maintain in a stable state. The team addressed this by precisely engineering the interface where TiO₂ and MoSe₂ meet, ensuring a continuous transfer of electrons from TiO₂ to MoSe₂. This approach stabilized the otherwise unstable 1T-MoSe₂ structure and enhanced both the activity and stability of the catalyst.

Platinum nanoparticles were also incorporated to rapidly collect light-generated electrons and accelerate the reduction reaction. In the resulting structure, MoSe₂ creates favorable conditions for CO2 reactions while platinum facilitates electron transfer — the two co-catalysts working in a mutually complementary fashion.

The photocatalyst recorded a methane output of 17.81 μmol/g in a light-concentrating reactor, roughly three times higher than under standard light irradiation conditions and about 65 times higher than conventional TiO₂ photocatalysts. Through experiments and theoretical calculations, the team confirmed that the increased photon supply from light concentration and efficient electron transfer at the catalyst interface are the key factors driving improved methane production.

"This technology can serve as a core catalyst for an artificial photosynthesis system that produces methane fuel using only sunlight, water and carbon dioxide — with no additional external energy input," In said. "Going forward, it can be applied to carbon capture and utilization facilities that capture and convert CO2 at emission sources, contributing to carbon neutrality."

The study, supported by the National Research Foundation of Korea's Nano Future Materials Source Technology Development project, was published in the journal Applied Catalysis B: Environment and Energy.